This show is fantastic. Season 1 was good. Season 2 is really good. Give it a try. I don't recommend bad shows.
2 books were stuffed into 8 episodes in season 2. It is pretty much non-stopped and better overall than season 1.
Yes it is from a book series called the Saxon Tales by Bernard Cornwell. It is also based on actual events as well. Bernard Cornwell is one of the premiere authors in the historical fiction genre. All of the battles were documented battles and he tries to be as accurate as possible in those regards. As an example, the main character Uthred, is a fictional character that manages to be in every major battle during the creating of England. In his Holy Grail series, Tomas manages to be in every major battle to begin the Hundred Year War. In his Sharpe series, Sharpe manages to be in every major battle during the Napoleanic wars, and so on.
He will most likely start showing up in season 3. Aethelfled is more important at this point of the story.